Biochar-based functional materials for the abatement of emerging pollutants from aquatic matrices.

Biochar has emerged as a versatile and efficient multi-functional material, serving as both an adsorbent and catalyst in removing emerging pollutants (EPs) from aquatic matrices. However, pristine biochar's catalytic and adsorption capabilities are hindered by its poor surface functionality and small pore size. Addressing these limitations involves the development of functionalized biochar, a strategic approach aimed at enhancing its physicochemical properties and improving adsorption and catalytic efficiencies. Despite a growing interest in this field, there is a notable gap in existing literature, with no review explicitly concentrating on the efficacy of biochar-based functional materials (BCFMs) for removing EPs in aquatic environments. This comprehensive review aims to fill this void by delving into the engineering considerations essential for designing BCFMs with enhanced physiochemical properties. The focus extends to understanding the treatment efficiency of EPs through mechanisms such as adsorption or catalytic degradation. The review systematically outlines the underlying mechanisms involved in the adsorption and catalytic degradation of EPs by BCFMs. By shedding light on the prospects of BCFMs as a promising multi-functional material, the review underscores the imperative for sustained research efforts. It emphasizes the need for continued exploration into the practical implications of BCFMs, especially under environmentally relevant pollutant concentrations. This holistic approach seeks to contribute to advancing knowledge and applying biochar-based solutions in addressing the challenges posed by emerging pollutants in aquatic ecosystems.

Insights into the response of electroactive biofilm with petroleum hydrocarbons degradation ability to quorum sensing signals.

Bioelectrochemical technologies based on electroactive biofilms (EAB) are promising for petroleum hydrocarbons (PHs) remediation as anode can serve as inexhaustible electron acceptor. However, the toxicity of PHs might inhibit the formation and function of EABs. Quorum sensing (QS) is ideal for boosting the performance of EABs, but its potential effects on reshaping microbial composition of EABs in treating PHs are poorly understood. Herein, two AHL signals, C4-HSL and C12-HSL, were employed to promote EABs for PHs degradation. The start-times of AHL-mediated EABs decreased by 18-26%, and maximum current densities increased by 28-63%. Meanwhile, the removal of total PHs increased to over 90%. AHLs facilitate thicker and more compact biofilm as well as higher viability. AHLs enhanced the electroactivity and direct electron transfer capability. The total abundance of PH-degrading bacteria increased from 52.05% to 75.33% and 72.02%, and the proportion of electroactive bacteria increased from 26.14% to 62.72% and 63.30% for MFC-C4 and MFC-C12. Microbial networks became more complex, aggregated, and stable with addition of AHLs. Furthermore, AHL-stimulated EABs showed higher abundance of genes related to PHs degradation. This work advanced our understanding of AHL-mediated QS in maintaining the stable function of microbial communities in the biodegradation process of petroleum hydrocarbons.

Acclimation of electroactive biofilms under different operating conditions: comprehensive analysis from architecture, composition, and metabolic activity.

Electroactive biofilms (EABs) have aroused wide concern in waste treatment due to their unique capability of extracellular electron transfer with solid materials. The combined effect of different operating conditions on the formation, microbial architecture, composition, and metabolic activity of EABs is still unknown. In this study, the impact of three different factors (anode electrode, substrate concentration, and resistance) on the acclimation and performance of EABs was investigated. The results showed that the shortest start-up time of 127.3 h and highest power density of 0.84 W m-2 were obtained with carbon brush as electrode, low concentration of substrate (1.0 g L-1), and 1000 Ω external resistance (denoted as N1). The EABs under N1 condition also represented strongest redox capacity, lowest internal resistance, and close arrangement of bacteria. Moreover, the EABs cultured under different conditions both showed similar results, with direct electron transfer (DET) dominated from EABs to anode. Microbial community compositions indicated that EABs under N1 condition have lowest diversity and highest abundance of electroactive bacteria (46.68%). Higher substrate concentration (3.0 g L-1) promoted the proliferation of some other bacteria without electroactivity, which was adverse to EABs. The metabolic analysis showed the difference of genes related to electron transfer (cytochrome C and pili) and biofilm formation (xap) of EABs under different conditions, which further demonstrated the higher electroactivity of EABs under N1. These results provided a comprehensive understanding of the effect of different operating conditions on EABs including biofilm formation and electrochemical activity.

Bioaugmentation enhance the bioremediation of marine crude oil pollution: Microbial communities and metabolic pathways.

Bioaugmentation is an effective strategy used to speed up the bioremediation of marine oil spills. In the present study, a highly efficient petroleum degrading bacterium (Pseudomonas aeruginosa ZS1) was applied to the bioremediation of simulated crude oil pollution in different sampling sites in the South China Sea. The metabolic pathways of ZS1 to degrade crude oil, the temporal dynamics of the microbial community response to crude oil contamination, and the biofortification process were investigated. The results showed that the abundance and diversity of the microbial community decreased sharply after the occurrence of crude oil contamination. The best degradation rate of crude oil, which was achieved in the samples from the sampling site N3 after the addition of ZS1 bacteria, was 50.94% at 50 days. C13 alkanes were totally oxidized by ZS1 in the 50 days. The degradation rate of solid n-alkanes (C18-C20) was about 70%. Based on the whole genome sequencing and the metabolites analysis of ZS1, we found that ZS1 degraded n-alkanes through the terminal oxidation pathway and aromatic compounds through the catechol pathway. This study provides data support for further research on biodegradation pathways of crude oil and contributes to the subsequent development of more reasonable bioremediation strategies.

Insights into the effects of operating parameters on sulfate reduction performance and microbial pathways in the anaerobic sequencing batch reactor.

Sulfate-reducing bacteria (SRB)-based anaerobic process has aroused wide concern in the treatment of sulfate-containing wastewater. Chemical oxygen demand-to-sulfate ratio (COD/SO42-) and HRT are two key factors that affect not only the anaerobic treatment performance but also the activity of SRB. In this study, an anaerobic sequencing batch reactor was constructed, and the effects of different operating parameters (COD/SO42-, HRT) on the relationship of sulfate (SO42-) reduction performance, microbial communities, and metabolic pathways were comprehensively investigated. The results indicated that the SO42- removal rates could achieve above 95% under different operating parameters. Bioinformatics analysis revealed that microbial community changed with reactor operation. At the genus level, the enrichment of Propionicclava and Peptoclostridium contributed to the establishment of a homotrophic relationship with Desulfobulbus, the dominant SRB in the reactor, which indicated that they took vital part in maintaining the structural and functional stability of the bacterial community under different operating parameters. In particular, an increasing trend of the relative abundance of functional genes encoding dissimilatory sulfate reduction was detected with the increase of COD/SO42-, which indicated high SO42- reduction potentials. This knowledge will help to reveal the mechanism of the effect of operating parameters on the anaerobic sulfate removal process, thus providing effective guidance for the targeted regulation of anaerobic sequencing batch bioreactors treating SO42--containing wastewater.

Study on the Changes in Immobilized Petroleum-Degrading Bacteria Beads in a Continuous Bioreactor Related to Physicochemical Performance, Degradation Ability, and Microbial Community.

Continuous bioreactors for petroleum degradation and the effect factors of these bioreactors have rarely been mentioned in studies. In addition, indigenous bacteria living in seawater could influence the performance of continuous bioreactors with respect to petroleum degradation in practice. In this paper, a bioreactor fitted with immobilized petroleum-degrading bacteria beads was designed for further research. The results indicated that the diesel degradation rate of the bioreactor could remain above 50% over 27 days, while degradation performance decreased with bioremediation time. Intriguingly, the diameters of immobilized petroleum-degrading bacteria beads were reduced by 32.49% after 45 days remediation compared with the initial size of the immobilized petroleum-degrading bacteria beads. Change in immobilized petroleum-degrading bacteria beads was considered to correlate remarkably with reduced degradation efficiency. Therefore, this paper will be helpful for further study and improvement of bioreactors in the practical context of oil-spill accident recovery.

Insight of the bio-cathode biofilm construction in microbial electrolysis cell dealing with sulfate-containing wastewater.

Signaling molecules are useful in biofilm formation, but the mechanism for biofilm construction still needs to be explored. In this study, a signaling molecule, N-butyryl-l-Homoserine lactone (C4-HSL), was supplied to enhance the construction of the sulfate-reducing bacteria (SRB) bio-cathode biofilm in microbial electrolysis cell (MEC). The sulfate reduction efficiency was more than 90% in less time under the system with C4-HSL addition. The analysis of SRB bio-cathode biofilms indicated that the activity, distribution, microbial population, and secretion of extracellular polymers prompted by C4-HSL, which accelerate the sulfate reduction, in particular for the assimilatory sulfate reduction pathway. Specifically, the relative abundance of acidogenic fermentation bacteria increased, and Desulfovibrio was co-metabolized with acidogenic fermentation bacteria. This knowledge will help to reveal the potential of signaling molecules to enhance the SRB bio-cathode biofilm MEC construction and improve the performance of treating sulfate-containing wastewater.

Petroleum spill bioremediation by an indigenous constructed bacterial consortium in marine environments.

In the process of marine oil spill remediation, adding highly efficient oil degrading microorganisms can effectively promote oil degradation. However, in practice, the effect is far less than expected due to the inadaptability of microorganisms to the environment and their disadvantage in the competition with indigenous bacteria for nutrients. In this article, four strains of oil degrading bacteria were isolated from seawater in Jiaozhou Bay, China, where a crude oil pipeline explosion occurred seven years ago. Results of high-throughput sequencing, diesel degradation tests and surface activity tests indicated that Peseudomonas aeruginosa ZS1 was a highly efficient petroleum degrading bacterium with the ability to produce surface active substances. A diesel oil-degrading bacterial consortium (named SA) was constructed by ZS1 and another oil degrading bacteria by diesel degradation test. Degradation products analysis indicated that SA has a good ability to degrade short chain alkanes, especially n-alkanes (C10-C18). Community structure analysis showed that OTUs of Alcanivorax, Peseudomona, Ruegeria, Pseudophaeobacter, Hyphomonas and Thalassospira on genus level increased after the oil spill and remained stable throughout the recovery period. Most of these enriched microorganisms were related to known alkane and hydrocarbon degraders by the previous study. However, it is the first time to report that Pseudophaeobacter was enriched by using diesel as the sole carbon source. The results also indicated that ZS1 may have a dominant position in competition with indigenous bacteria. Oil pollution has an obvious selective effect on marine microorganisms. Although the oil degradation was promoted after SA injection, the recovery of microbial community structure took a longer time.

Fabrication of a Cation-Exchange Membrane via the Blending of SPES/N-Phthaloyl Chitosan/MIL-101(Fe) Using Response Surface Methodology for Desalination.

In the present work, a novel mixed matrix cation exchange membrane composed of sulfonated polyether sulfone (SPES), N-phthaloyl chitosan (NPHCs) and MIL-101(Fe) was synthesized using response surface methodology (RSM). The electrochemical and physical properties of the membrane, such as ion exchange capacity, water content, morphology, contact angle, fixed ion concentration and thermal stability were investigated. The RSM based on the Box-Behnken design (BBD) model was employed to simulate and evaluate the influence of preparation conditions on the properties of CEMs. The regression model was validated via the analysis of variance (ANOVA) which exhibited a high reliability and accuracy of the results. Moreover, the experimental data have a good fit and high reproducibility with the predicted results according to the regression analysis. The embedding of MIL-101(Fe) nanoparticles contributed to the improvement of ion selective separation by forming hydrogen bonds with the polymer network in the membrane. The optimum synthesis parameters such as degree of sulfonation (DS), the content of SPES and NPHCs and the content of MIL-101(Fe) were acquired to be 30%, 85:15 and 2%, respectively, and the corresponding desalination rate of the CEMs improved to 136% while the energy consumption reduced to 90%. These results revealed that the RSM was a promising strategy for optimizing the preparation factors of CEMs and other similar multi-response optimization studies.

Study on the preparation conditions and degradation performance of an efficient immobilized microbial agent for marine oil pollution.

In the process of handling marine oil spills accidents, the biological method has attracted wide attention due to its low cost and no secondary pollution. However, in the process of practical application, there are problems such as low microbial density and great influence of environmental factors when the oil is treated by spraying microorganisms on the sea surface. This study used immobilized microorganism technology to solve the above-mentioned problems. In this study, the bacteria immobilized on cinnamon shell (CS) with good degradation performance were obtained by optimizing preparation conditions. Under the optimal conditions of sodium alginate (SA) concentration of 4.57%, CS concentration of 1.28%, and the CaCl2 concentration of 2.45%, the degradation rate of diesel in 5 days reached 74.04%. The reusability of immobilized microbial agents was further studied. The study designed three cycles of repeated degradation experiments. The results showed that the degradation rate of diesel can still reach 60.12% after three times of reuse, which indicated the reusability of the immobilized microbial agents was excellent. The decrease in degradation rate of diesel was mainly related to the fragmentation of immobilized microbial agents and the decrease in microbial biomass.

Influential Mechanism of Natural Organic Matters with Calcium Ion on the Anion Exchange Membrane Fouling Behavior via xDLVO Theory.

The fouling mechanism of the anion exchange membrane (AEM) induced by natural organic matter (NOM) in the absence and presence of calcium ions was systematically investigated via the extended Derjaguin-Landau-Verwey-Overbeek (xDLVO) approach. Sodium alginate (SA), humic acid (HA), and bovine serum albumin (BSA) were utilized as model NOM fractions. The results indicated that the presence of calcium ions tremendously aggravated the NOM fouling on the anion exchange membrane because of Ca-NOM complex formation. Furthermore, analysis of the interaction energy between the membrane surface and foulants via xDLVO revealed that short-range acid-base (AB) interaction energy played a significant role in the compositions of interaction energy during the electrodialysis (ED) process. The influence of NOM fractions in the presence of calcium ions on membrane fouling followed the order: SA > BSA > HA. This study demonstrated that the interaction energy was a dominating indicator for evaluating the tendency of anion exchange membranes fouling by natural organic matter.

Optimization and mechanism of oily sludge treatment by a novel combined surfactants with activated-persulfate method.

Recently, the extensive discharge of oily sludge, due to excessive use of fossil oil, has become a serious worldwide concern, as it leads to serious environmental pollution and even threat human health. However, the complex properties and compositions of oily sludge make it difficult for the treatment of oily sludge. This study proposed a novel method of combined degradation of oily sludge by surfactants with activated-persulfate, and analyzed the degradation efficiency and degradation pathway. The organics in oil sludge were eluted by surfactant, and the residual oil difficult to be eluted was further oxidized by activated persulfate. The combined method significantly improved the degradation efficiency of oily sludge, and the removal rate reached 94.6 ± 2.8%, and the oil content of the residual oily sludge was 0.57%, which had reached the discharge standard. The mechanism analysis indicated that surfactant could increase the solubility of oil by reducing the surface tension, and the hydroxyl radical and sulfate radical generated by activated persulfate could degrade the complex organic matters into small molecule matters, achieving efficient degradation of oil sludge. This work demonstrated a new avenue for the efficient and cost-effective treatment of oily sludge, opening an environmentally friendly treatment concept.

Analyses of community structure and role of immobilized bacteria system in the bioremediation process of diesel pollution seawater.

Immobilized bacteria system plays an important role during degradation process in oil contaminated seawater. Although the immobilized bacteria system can be recycled to avoid pollution after remediation, it remains an open question on whether or not the secondary pollution occurs during the degradation process. Additionally, the research on the role of immobilized bacteria system in the process of oil removal is not clear enough. In this study, both the diesel degradation rate of diesel by immobilized bacteria system and changes in marine microbial community structure were determined to explore the role of immobilized bacteria system. The immobilized bacteria system was added to the diesel polluted seawater (1% diesel) for 30 days. The degradation performance was investigated during the process, and the microbial community structure was analyzed simultaneously. The results illustrated that the degradation rate of diesel by immobilized bacteria system reached 78.39% after 30 days, and Alcanivorax (59.09%), Achromobacter (24.34%) and Thalassospira (9.84%) were the dominant genera in the immobilized bacteria system. The addition of immobilized bacteria system increased the content of nitrogen and phosphorus, and then promoted the growth of oil-degrading bacteria. Thus, functional genes related to oil degradation increased. Additionally, there was little difference in the microbial composition between the treated seawater and the unpolluted seawater. Based on all results, it can be inferred that immobilized bacteria system triggered and stimulated diesel degradation process. This study provides a promising way to improve the removal of oil, and provides theoretical support for the wide application of immobilized microorganism technology.

Opposite impacts of chemical oxidation for ofloxacin adsorption on activated carbon and carbon nanotubes.

The adsorption of ofloxacin (OFL) on oxidized activated carbon (AC) and carbon nanotube (CNT) are compared, focusing on the differences in carbon structures. Chemical oxidation of carbonaceous materials inhibited OFL adsorption to AC, but enhanced their adsorption to CNT. The higher number of oxygen-containing functional groups facilitated the interaction of the material with water molecules, causing the blockage of AC inner pore. However, the dispersion of oxidized CNT enhanced due to its increased hydrophilicity, resulting in the exposure of some new adsorption sites, as identified by the 1H NMR relaxometry measurement. The adsorption kinetics of OFL on AC indicated that the contributions of slow adsorption and equilibrium time increased after AC oxidation. However, the equilibrium time of the fast adsorption of OFL on CNT shortened after CNT oxidation. These results indicated that the pore of AC was blocked by water cluster and the accessibility of adsorption sites on oxidized CNT was enhanced due to dispersion. This study emphasizes that the structural differences among carbonaceous materials control the oxidation effects on their adsorption characteristics for OFL.

New insights into the different adsorption kinetics of gallic acid and tannic acid on minerals via 1H NMR relaxation of bound water.

The slower adsorption of lower molecular weight organic molecules remains poorly understood. This study investigated the adsorption kinetics of gallic acid (GA) and tannic acid (TA) on kaolinite (Kao), montmorillonite (Mon) and hematite (Hem), with an emphasis on the role of the bound water on the minerals. The lower adsorption of TA and GA on Kao than on Mon attributed to the lower specific surface area of Kao. Because of the electrostatic attraction, the adsorption of TA and GA on Hem was higher than that on Mon, even the specific surface area of the former was much lower than that of the later. The adsorption rates of TA on the three minerals were generally two orders of magnitude higher than those of GA. The adsorption kinetics of GA was strongly diffusion dependent; however, the diffusion process had limited influence on TA adsorption kinetics. The decreased c values of the intraparticle diffusion model of GA with increasing ionic strength provided additional direct evidence for the diffusion-dependent adsorption and the reduced hindrance by bound water via hydration layer compression. However, hydration layer compression had no effect on TA adsorption kinetics. The reduced 1H NMR relaxation rate of bound water indicated that the bound water quantity on minerals decreased with increasing ionic strength, which proved the occurrence of hydration layer compression. This study highlighted the importance of bound water and the relative sizes of organic molecules in the adsorption kinetics of organic compounds on minerals, which should be carefully considered for their environmental fate studies.

Adsorption of chromium by functionalized metal organic frameworks from aqueous solution.

Based on Cu-BTC metal-organic framework, thiol-functionalized and amino functionalized materials were prepared by the modified Stöber method. Then, the Cu3(BTC)2 and the functionalized materials were characterized by means of X-ray diffraction, SEM-EDS and FT-IR analysis. The adsorption properties of two materials for Cr(VI) were investigated. Both functionalized materials show good adsorption under acidic conditions. Through adsorption model analysis, the adsorption of Cr(VI) by the two materials were more in line with the pseudo-second-order kinetic equation. The adsorption capacities of Langmuir isothermal fitting were 15.17 mg g-1 and 7.17 mg g-1, respectively. During the adsorption process, the functionalized material does not swell and is insoluble in water. After five adsorption-desorption cycles, the adsorption capacity is basically constant and the material can be reused. The results show that the above two functionalized MOFs have good application prospects in the adsorption and removal of heavy metal Cr(VI) in aqueous solution.

Evaluation of response of dynamics change in bioaugmentation process in diesel-polluted seawater via high-throughput sequencing: Degradation characteristic, community structure, functional genes.

Identification of microorganisms that contribute to the whole microbial community is important. In this study, dynamic changes in bioaugmentation process in diesel-polluted seawater collected from two different sites were assessed via simulation experiments. Ultraviolet spectrophotometry and analysis using the molecular operating environment software revealed that the degradation rate of diesel due to bioaugmentation was higher than 70 % after 45 days because of the formation of hydrogen bonds among biosurfactants and diesel components. Community structure and functional genes were analysed via high-throughput sequencing. Results showed that community diversity recovered during bioaugmentation. Principal coordinate analysis showed that the difference in microbial community between the two sites was considerably smaller than that when diesel was added and bioaugmentation was conducted. After bioaugmentation, the main families playing key roles in degradation that became dominant were Alcanivoracaceae, Rhodobiaceae, and Rhodospirillaceae. Moreover, the abundance of functional genes remarkably increased at two different sites.

Preparation, optimization and reusability of immobilized petroleum-degrading bacteria.

In the remediation of marine pollution, it is important to effectively degrade pollutants and reuse petroleum-degrading bacteria. In order to obtain more effective biodegradability and reusability, an immobilized bacteria combination with petroleum-degrading bacteria, sodium alginate (SA) and biochar by adsorption-embedding method was systematically analysed. The results indicated that the immobilized bacteria had good mechanical properties and the degradation rate was 51% when the straw (CS) was 3%, the SA and CaCl2 were 4.5% and 6%, respectively. Besides, SA-CS-DM-PVA has the highest degradation rate and the lowest broken rate, above 51% and below 6.1% respectively. The optimum dosage of the modified immobilized bacteria was 132, degradation time was 5d, and reuse frequency was 4 times. Moreover, immobilized bacteria characterized by scanning electron microscopy (SEM), results showed that there were more pores on the surface after degradation, and the carrier was exposed. Therefore, the modified immobilized bacteria with good degradability and reusability, have good application prospects in the treatment of marine oil pollution.

Physiological and morphological responses and tolerance mechanisms of Isochrysis galbana to Cr(VI) stress.

The effects of the initial concentrations of Cr(VI) on chlorophyll-a (Chl-a), soluble protein and ultrastructure were investigated. Results showed that <0.5 and >1.0 mg L-1 Cr(VI) stimulated and inhibited the growth of Isochrysis galbana, respectively. The tolerance mechanisms of I. galbana to Cr(VI) included the following: (1) increased activities of superoxide dismutase (SOD) and peroxidase (POX) for peroxidative damage resistance, (2) accumulation of Cr(VI) on the cell surface and inside the cell for detoxification and (3) conversion of intracellular Cr(VI) to less toxic Cr(III) as indicated by X-ray photoelectron spectroscopy (XPS) results. Cr(VI) enrichment by I. galbana may cause damage to marine ecology and human bodies through the food chain. The tolerance mechanisms of I. galbana to Cr(VI) may be potentially used to treat low-concentration Cr(VI) wastewater. Therefore, the responses and tolerance mechanisms of I. galbana to Cr(VI) must be further studied.

Systematic degradation mechanism and pathways analysis of the immobilized bacteria: Permeability and biodegradation, kinetic and molecular simulation.

In order to effectively improve the degradation rate of diesel, a systematic analysis of the degradation mechanism used by immobilized bacteria is necessary. In the present study, diesel degradation mechanisms were assessed by analyzing permeability, biodegradation, adsorption kinetics, and molecular simulation. We found that bacteria immobilized on cinnamon shells and peanut shells degraded relatively high amounts of diesel (69.94% and 64.41%, respectively). The primary degradation pathways used by immobilized bacteria included surface adsorption, internal uptake, and biodegradation. Surface adsorption was dominant in the early stage of degradation, whereas biodegradation was dominant in later stages. The diesel adsorption rate of the immobilized bacteria was in agreement with the pseudo second-order kinetic model. The immobilized bacteria and diesel interacted through hydrogen bonds.